This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present embodiments that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Tuners and tuner systems, such as those used in satellite receiver set top boxes, have increasingly become more complex. For instance, multiple tuners can be used to simultaneously provide separate received signals to hard disk drives for recording and storage and to external display devices such as televisions as well as to other rooms in a home. Further, satellite service providers have increased capability by providing additional channel capacity as well as new signal modulation formats. The increased signal capability may require the tuners and tuner systems to operate with signals having a large variation in performance requirements and input conditions. The additional complexity and capability has subsequently strained the design requirements for the tuners and tuner systems.
In order for the tuner system used in a set top box to operate effectively, each tuner in the tuner system must be able to operate and receive signals independently and free of operational interference from signals supplied to the other tuners. The operation must be maintained regardless of whether the input signals originate from a common signal source or from separate streams or separate sources. One current approach to maintain effective tuner operation is to incorporate circuits and design requirements that provide electrical signal isolation between the tuners. Electrical signal isolation prevents one tuner from receiving a signal meant to be provided to another tuner in the set top box. The circuits and design requirements result in reducing or eliminating the coupling of electrical signal energy from one signal path into another, commonly referred to as crosstalk.
In some worst case design conditions, the crosstalk requirements between two tuners in a tuner system may require that electrical signal isolation be as high as seventy (70) decibels (dB). A requirement for such a high level of electric signal isolation results in a costly implementation as well as a technically challenging design. Unacceptable crosstalk levels may only exist under certain signaling conditions and crosstalk issues may be more easily eliminated in signaling conditions such as when only one signal stream is provided. It may be possible that crosstalk even in the remaining signaling conditions may be able to be prevented or controlled in some manner if the crosstalk can be detected. Therefore there is a need for an effective method and apparatus for determining and, when possible, preventing signal crosstalk between tuners in a tuner system.